Automatic stitch length adjusting mechanism



ND mmm QNN NNM wwm .mwm WN g Q m 3n mm wwn C. W. JOHNSON Original Filed Aug. 12, 1939 wNMKNN AUTOMATIC STITCH LENGTH ADJUSTING MECHANISM Jan. 16, 1%51 IHVENTOR CARL W. JOHNSON BY Y ATTORNEY.

3 bar I35 attached thereto is in a closed uni-directional path. This movement can be separated into two main motions, i. e., an up and down or vertical motion, and a back and forth or horizontal motion. The up and down movement of arm I28 is imparted by acam III) with which c'oacts a cam follower I23 provided on an arm I33 of a bell crank lever loosely mounted on shaft I2Ia. Th other arm I3I of the bell crank lever is connected to one end of an adjustable link I32 which in turn is connected to a depending portion I33 of arm I28. Cam follower I29 is maintained in tracking relationship with cam III] by means of a spring 34!! having one end attached to a pin 342 in member I 2I, and the other end attached to a pin 344 in frame I30.

Cam III; is mounted on a shaft 32I to which is,

fixed a sprocket 329 driven from a suitable sprocket and chain (not shown)"from the main drive shaft of the sewing machine.

The back and forth or horizontal movement of arm I28 is eifected by means of a crank pin III mounted on cam IIO provided with a roller The lower portion of arm 329 is provided with an elongated slot 33I attached to engage thumb screw 330. By loosening the thumb screw 330, arni329 may be moved relative to lever 328 and in so doing shift the position of slot I29 in slotted member I2I resulting in more or less movement of arm I28 and consequently longer or shorter stitches;

The cam 325 has a high portion 332 and a low portion 333, the surface 332 being consid erably longer than 333 and therefore when it engages follower 32'! it holds the slotted head of stitch control member I2I in a position to produce a long stitch. As the follower 321 rides off H2 running in elongated slot H3 in the lower end of lever I I4 fulcrumed to the horizontal arm ofibell crank lever I I5. A washer I I2a on crank pin III maintains roller" H2 in slot I I3. Lever H4 is provided with a stud IIS carrying a fol- :lower II9 engaging a slot I23 in a slotted mem- I2Ia. An arm 328, loosely mounted on shaft I2Ia, carries a cam follower I2 i on shaft "-321. running on cam 326 and held in engagement therewith by means of a spring 346 having one end attached to a pin 343 secured to arm 328 and the other end attach d. to a suitable pin (not shown) in the framelflfl.

' trol the extent ofvertical movement of lever H4 and-the amount of horizontal movement of arm The purpose of the slotted member I21 and arm-328 which is oscillated'by'cam 326 isto con- I28. In this way the length of each stitch made can be" controlled. The amount of back and forth or horizontal movement of arm I28 and feed bar 135 supported thereon depends upon the position of slot I23 in member I2I. By

: changing the angular relationship of slot I2I] in -to the setting of member I2I.

subsequent stitching operations,

the stitches made can be longer or shorter according Th more slot I20-is turned toward the vertical, the, greater E-WiI]. be the fe:ding motion of feed-bar I due ..to,the fact that lever- II4 pivoted upon lever II51will be raised a greater amount; so also lever II 5 will be rocked a proportionately greater amount. If it is desired to decrease the ampliv..,tude of feed bar I35, slotted member I2I will zontal.

be so adjusted in the opposite direction so that 1 or the demands of a' given piece of work being sewed or decorated.

- The invention above described may be varied in construction within the scope of the claims, for the particular device, selected to illustrate the invention, is but one of' many possible concrete embodiments of the same. It is not, therefore, to be restricted to the precise detailsof the structure shown and described. What I claim is:

1. In a: sewing machine, a work support, means for feeding work to be sewed along saidsupport including a feed bar, and mechanism for varying the amount of movement of said means, said mechanism comprising a lever associated with said bar, a second lever pivoted on said firstnamed lever, means for oscillating said second "lever, a follower carried by said second lever,"a

slotted member normally engaging said follower,

1 and means for automatically shifting the position of said slotted member after the formation of each stitch to vary the extent of movement of said lever, said last-named means including a f rotating cam and an element associated with said slotted member and coacting with said cam to alternately increase or decrease theamount the slot therein will be moved towards the hori- Since lever H5 is connected to link I21 connected to material feed arm I23; the resulting back and forth or horizontal motion imparted to arm I23 can be varied thereby making. it possible to adjust the length and make longer or shorter stitches as required. r

The mechanism for automatically producing alternate short and long stitches is constructed --andoperates as follows:"

A gear 322 fixed on shaft.32I meshes with and drives agear 323 and -its attached gear 324 loosely mounted on shaft I2 Ia; .fwhile gear 324 in turn drives 'a gear 325' and a cam 32$ loosely mounted on shaft 32 I.

.athis manner the gearing 322, 323,324 and 325 .iclaniped on shaft'l2la by a thumb screw 330.-

.drives cam 326 at one-half the speed of cam IIII. Lever 328 is adjustably attached to arm 329 of horizontal movement of said bar. I

2.'In a sewing machine, the combination with .a work support, of mechanism for feeding to be sewed along said support, means associ with said mechanism for adjusting the lengthjpf stitch to be made, said means including asloted stitch length control member, means for adjusting the angular position of said slotted stitch length control member to make alternate 'long and short stitches, and cam operated means for moving said slotted stitch length control member after. eachstitch isformed to 'modifythe "movement of said feeding mechanism and thereby cause stitches of varying length to be formflld.

3. In a sewing machine, work support,.,means for feeding work to be sewed along said support including awork feed her, and 'mechanism' f or varying; the amount of movement of said means, said mechanism comprising a lever associated with said bar, a second lever pivoted on said firstnamed 'leveig'means foroscillating said-- second lever, a, follower carried by said second leven'fla slotted member normally engaging said follower, means for shifting the position of said slotted member to vary the extent of movement of said lever, said last-named means including a cam, a shaft, an arm loose on said shaft, an adjusting arm fixed to said shaft, a cam follower on said loose arm tracking said cam, and adjusting means carried by said fixed arm for securing said arms together in predetermined position relative to said shaft and said loose arm to thereby adjust the length of alternate stitches formed.

4. In a sewing machine, means for feeding the work to form a predetermined normal length stitch, mechanism for changing the length of travel of said feeding means to change the length of stitch formed, said mechanism comprising a feed bar, means for imparting a normal closed path of movement to said bar, a stitch length control member, means for mounting said memsaid bar to-feed a predetermined normal length of work, and means for automatically turning said member after the formation of each stitch to cause said bar to feed a greater or lesser length of work and thereby Vary the length of stitch formed.

5. In a sewing machine, means for feeding the work to form a predetermined normal length stitch, mechanism for changing the length of travel of said feeding means to change the length of stitch formed, said mechanism comprising a feed bar, means for imparting a normal closed path of movement to said bar, including means for imparting vertical motion to said bar, and means for imparting horizontal motion to said bar, an oscillatable stitch length control mem- 6 ber, means for mounting said member for oscillator movement, means for adjusting the angular position of said member to cause said bar to feed a predetermined normal length of work, and means for automatically turning said member after the formation of each stitch to cause said bar to feed a greater or lesser length of work and thereby vary the length of stitch formed.

6. In a sewing machine, a work support, a traveling feed bar associated with said support, mechanism for imparting to said feed bar movement in a unidirectional closed path including an oscillatable slotted control member, a lever connected to said bar, a cam follower on said lever and tracking said slot in said member, means for adjusting the angular position of said member. to determine the horizontal movement of said feed bar for producing normal stitches, means for maintaining said member in said adjusted position during operation of said machine, and selective means for moving said slotted member after the formation of each alternate stitch whereby the angular relationship of said slot and said follower is changed and the travel of said bar decreased to form shorter stitches.

' CARL W. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 29,268 Hicks July 24, 1860 1,259,996 Kinder Mar. 19, 1918 1,346,120 Francis July 13, 1920 2,124,033 Hand July 19, 1938 

